Magnetic storage element, recording method using the same, and magnetic storage device

ABSTRACT

A magnetic storage element capable of recording with a small magnetic field and retaining information stably and a recording method thereof, and a magnetic storage device having the magnetic storage element and capable of simplifying a drive circuit thereof are provided. The magnetic storage element comprises a storage layer, a non-magnetic layer and a pinned layer. The storage layer is composed of directly stacked first magnetic layer mainly composed of a transition metal and second magnetic layer mainly composed of a rare-earth metal; and a magnetization amount of the first magnetic layer is smaller than that of the second magnetic layer at a room temperature. A magnetization state of one direction is recorded by heating and applying a magnetic field to the storage layer, and a magnetization state of the other direction is recorded by making magnetic coupling work between the first magnetic layer and the pinned layer by heating.

CROSS REFERENCES TO RELATED APPLICATIONS

The present document is based on Japanese Priority Document JP2002-333801, filed in the Japanese Patent Office on Nov. 18, 2002, theentire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic storage element preferablyapplicable to a non-volatile memory, a recording method using the same,and a magnetic storage device using the magnetic storage element.

2. Description of Related Art

In information apparatuses such as computers, a DRAM which is operableat a high speed and having a large storage density is widely used asrandom access memories therefor. A DRAM is however classified as avolatile memory which cannot keep information when the power supply isinterrupted, so that there is a demand for non-volatile memory which cankeep information at any time.

One example of the non-volatile memory relates to a magnetic randomaccess memory (MRAM) which uses magnetic storage elements capable ofrecording information based on a magnetization state of a magneticmaterial (see non-patent document 1, for example).

[Non-Patent Document 1]

Nikkei Electronics, Feb. 12, 2001 (pp. 164-171)

SUMMARY OF THE INVENTION

Because trends for the future require for the MRAM to further raisedensity for a larger storage capacity, and to reduce size of themagnetic storage element composing the memory cells thereof.

The magnetic storage element used for the MRAM utilizes a demagnetizingfield generated by having the magnetic material being rectangular oroval to stabilize a magnetization state. The magnetic material, however,tends to increase its coercive force as the size thereof is reduced, andthis inevitably raises a coercive force also in the magnetic storageelements used for the MRAM with progress of the size reduction.

Depending on the increase of the coercive force along with the reductionin size of the magnetic storage element, a further larger magnetic fieldis required to be applied at the time of recording. In the MRAM, anelectric current (recording current) applied to a word line and a bitline generates a magnetic field to record on the magnetic storageelement and there is required a large amount of recording current.Accordingly, when a recording capacity of the MRAM is enlarged by havinga large number of elements by reducing the size of the magnetic storageelement, an amount of the consumption electric current of the MRAM isincreased. Therefore, in order to increase the storage capacity of theMRAM, it is desired that the coercive force of the magnetic storageelement is reduced to reduce the amount of recording current.

On the other hand, when the magnetic storage element is reduced in size,a coercive force to some extent large is required to stably holdrecorded information. Therefore, in the case of reducing the magneticstorage element in size, it is necessary to satisfy conflictingconditions, one for reducing the coercive force to reduce the recordingcurrent and the other for having a coercive force to some extent tostably hold the recorded information.

Furthermore, in the MRAM, using the magnetic field generated from theelectric current applied to the word line and the bit line, informationis recorded by changing a direction of the magnetization of the storagelayer of the magnetic storage element in accordance with a direction ofthe generated magnetic field. Accordingly, in order to change thedirection of the magnetization of the storage layer, it is necessary tochange the direction of the electric current. In view of this, since thenumber of combinations of the electrical potential supplied to both endsof the word line and the bit line becomes large and a drive circuitbecomes complicated, this brings an obstruction for having a higherstorage density.

In order to solve these conventional problems, in the present invention,there are provided a magnetic storage element capable of recording witha small magnetic field and of stably holding information and a recordingmethod thereof, and a magnetic storage device having the magneticstorage element and capable of recording with a small amount of arecording current and of stably storing the information and capable ofsimplifying a drive circuit thereof.

The magnetic storage element of the present invention comprises astorage layer for holding a magnetization state as information, anon-magnetic layer, and a pinned layer in which a direction of themagnetization is fixed. The storage layer is constituted by directlystacking a first magnetic layer mainly composed of a transition metaland a second magnetic layer mainly composed of a rare-earth metal, andat the room temperature, an amount of magnetization of the firstmagnetic layer is smaller than that of the second magnetic layer.

In addition, in the magnetic storage element of the present invention,it may be arranged so that the first magnetic layer among the first andsecond magnetic layers constituting the storage layer is disposed nearerto the pinned layer.

A recording method according to the present invention is used for amagnetic recording element comprising: a storage layer for holding amagnetization state as information, a non-magnetic layer and a pinnedlayer in which a direction of the magnetization is fixed, which arestacked, the storage layer is composed of a first magnetic layer mainlycomposed of a transition metal and a second magnetic layer mainlycomposed of a rare-earth metal which are directly stacked, in which amagnetization amount of the first magnetic layer is smaller than amagnetization amount of the second magnetic layer at a room temperature,wherein recording is carried out by heating the storage layer andapplying a magnetic field to the magnetic layer so as to record amagnetization state in a single direction on the magnetic layer, and byheating the storage layer to have a magnetic coupling work on the firstmagnetic layer and the pinned layer so as to record a magnetizationstate in the other direction on the storage layer.

A magnetic storage device the present invention comprises: a magneticstorage element which comprises a storage layer for holding amagnetization state as information, a non-magnetic layer and a pinnedlayer in which a direction of the magnetization is fixed, which arestacked, in which the storage layer is composed of a first magneticlayer mainly composed of a transition metal and a second magnetic layermainly composed of a rare-earth metal which are directly stacked, and amagnetization amount of the first magnetic layer is smaller than amagnetization amount of the second magnetic layer at a room temperature;a reader for reading out a relative magnetization between the storagelayer and the pinned layer depending on a change of a electricalresistance, a wiring for applying a current induced magnetic field inone direction to the storage layer, and a heater for heating the storagelayer.

In addition, in the magnetic storage apparatus of the present invention,the wiring may be electrically connected to the storage layer and mayalso function as a heater. Furthermore, in the magnetic storageapparatus of the present invention, in addition to the above-mentionedwiring, a second wiring may be provided so that the wiring and thesecond wiring function as the heater.

According to the structure of the above-described magnetic storageelement of the present invention, since the storage layer is composed ofthe first magnetic layer mainly composed of a transition metal and thesecond magnetic layer mainly composed of a rare-earth metal which aredirectly stacked, the magnetization amount of the first magnetic layeris smaller than that of the second magnetic layer at the roomtemperature, a direction of the magnetization of the whole storage layerbecomes the same as the direction of the magnetization of the secondmagnetic layer at the room temperature. As the storage layer is heatedand the temperature rises, the magnetization of the second magneticlayer becomes smaller and the magnetization of the whole storage layeralso becomes small. Therefore, it is possible to carry out recording bychanging the magnetization of the storage layer using a smaller magneticfield. In addition, since the storage layer, the non-magnetic layer andthe pinned layer are stacked to constitute the magnetic storage element,it is possible to generate a magnetic coupling between the pinned layerand the first magnetic layer mainly composed of the transition metal ofthe storage layer and to align the directions of the magnetization ofthe pinned layer and the magnetization of the first magnetic layer to bethe same, that is, in parallel. When the storage layer is further heatedto a higher temperature to further reduce the magnetization of thesecond magnetic layer mainly composed of the rare-earth metal. Thisresults in that the whole storage layer has very few magnetization or anextremely small magnetization so that the magnetic coupling is madeeffective. Accordingly, even if the magnetic field is not applied to thestorage layer, it is possible to align the directions of themagnetization of the pinned layer and the magnetization of the firstmagnetic layer to be the same (in parallel) and to make these directionsbe in anti-parallel at the room temperature.

In addition, in the above magnetic storage element of the presentinvention, when the first magnetic layer among the first magnetic layerand the second magnetic layer constituting the storage layer is disposednearer to the pinned layer, since the first magnetic layer mainlycomposed of the transition metal is disposed nearer to the pinned layer,it is possible to strengthen the interaction between the first magneticlayer and the pinned layer usually composed of a transition metal and anelectric current easily flows through the non-magnetic layer disposedbetween them so that reading of the magnetization state of the storagelayer can be performed easily.

According to the above recording method of a magnetic storage element ofthe present invention, by heating the storage layer and applying themagnetic field to the storage layer of the magnetic storage element ofthe present invention, a magnetization state of one direction isrecorded on the storage layer, and by heating the storage layer to havea magnetic coupling function on the first magnetic layer and the pinnedlayer so as to record a magnetization state in the other direction onthe storage layer, and when the magnetization state of the otherdirection is recorded on the storage layer, it is possible to carry outrecording owing to actions of the heating and the magnetic couplingwithout applying the magnetic field to the storage layer. Accordingly,the magnetic field applied to the storage layer can be fixed to the onehaving one direction which makes the magnetization state of the storagelayer in the direction.

According to the structure of the magnetic storage device of the presentinvention, since it comprises the above magnetic storage element of thepresent invention, the reader for reading out a relative magnetizationbetween the storage layer and the pinned layer depending on a change ofa electrical resistance, the wiring for applying a current inducedmagnetic field in one direction to the storage layer, the heater forheating the storage layer, it is possible to record on the magneticstorage element in accordance with the above-described recording method.That is, it is possible to record the magnetization state in the onedirection on the storage layer by heating the storage layer by theheater and applying the current induced magnetic field of the onedirection by making it flow through the wiring. In addition, by heatingthe storage layer by the heater and making the magnetic couplingeffective on the first magnetic layer and the pinned layer, it ispossible to record the magnetization state of the other direction on thestorage layer without making the electric current flow through thewiring for applying the current induced magnetic field.

Furthermore, in the case of the magnetic storage apparatus of thepresent invention having the wiring electrically connected to thestorage layer for also functioning as the heater, the electric currentflows from the wiring to the storage layer so that the current inducedmagnetic field effectively works on the storage layer. In addition, itbecomes easy to carry out heating and application of the magnetic fieldsimultaneously. In addition, in the magnetic storage apparatus of thepresent invention, in the case of having the second wiring in additionto the original wiring and constituting the heater with these wirings,it is possible to perform recording by selecting arbitrary magneticstorage element by selecting the wiring. Furthermore, since the heatercomprises two kinds of wirings, depending on a combination of theelectric currents to be supplied to these wiring, the heating conditioncan be changed so that the magnetization state recorded on the storagelayer can also be changed.

According to the present invention described above, it becomes possibleto record on the storage layer with a smaller magnetic field owing tothe heating than at the room temperature. In addition, at the roomtemperature, the magnetization of a storage layer becomes larger and sothe coercive force thereof than when it is heated so that recordedinformation is stably retained. Furthermore, by heating the storagelayer to make its temperature higher so that the magnetic coupling worksbetween the pinned layer and the first magnetic layer, by only heatingthe storage layer, even without applying the magnetic field to thestorage layer, it becomes possible to record the magnetization statehaving one direction on the storage layer. Therefore, only at the timeof recording the magnetization state of the other direction on thestorage layer, the magnetic field is to be applied to the storage layerand the magnetic field to be applied to the storage layer can have onlyone direction. Accordingly, the structure of the means for applying themagnetic field to the storage layer can be simplified.

Furthermore, according to the magnetic storage device of the presentinvention, since the electric current is supplied through the wiring forapplying the current induced magnetic field to the storage layer of themagnetic storage element and the magnetization state of one directioncan be recorded on the storage layer, and also, even without supplyingthe electric current to the wiring, the magnetization state of the otherdirection can be recorded on the storage layer, the electric currentshould have one direction only. Accordingly, in comparative of the caseof flowing the electric current through the wiring in both directions,the number of combinations of electrical potential supplied to both endsof the wiring can be reduced and the drive circuit for supplying theelectric current to the wiring can be simplified. Accordingly, itbecomes possible to simplify the structure of the magnetic storagedevice and to realize high density easily.

In particular, in the case of the magnetic storage apparatus of thepresent invention having the wiring electrically connected to thestorage layer for also functioning as heater, the current inducedmagnetic field effectively works on the storage layer so that recordingwith smaller electric current is made possible. In addition, in the caseof having the second wiring in addition to the original wiring andconstituting the heater with these wirings, it is possible to performrecording selecting arbitrary magnetic storage element by selecting thewiring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing a magnetic storage elementaccording to one embodiment of the present invention;

FIG. 2 is a detailed cross sectional view showing the vicinity of amagnetic tunnel junction element of FIG. 1.

FIG. 3A to FIG. 3D are views showing changes of a magnetization state ofthe storage layer of the magnetic storage element of the presentinvention in accordance with temperature change.

FIG. 4A to FIG. 4C are views explaining recording operations on themagnetic storage element.

FIG. 5A and FIG. 5B are also views explaining recording operations onthe magnetic storage element of the present invention.

FIG. 6 is a graph showing ratio of an amount of magnetization of thestorage layer at the room temperature and at other temperatures.

FIG. 7 is a view showing a measurement result of relationship betweenstrength of a magnetic field applied to the magnetic tunnel junctionelement of FIG. 2 and a tunnel resistance, in which FIG. 7A is ameasurement result at a room temperature, FIG. 7B is a measurementresult at 125° C. and FIG. 7C is a measurement result at 175° C.

FIG. 8 is a graph showing values of Hf and Hc at each temperature in themagnetic tunnel junction element of FIG. 2.

FIG. 9 is a view showing a measurement result of an inversionprobability of the magnetization with regard to a pulse current valuewhen a pulse current is applied to the magnetic tunnel junction elementof FIG. 2.

FIG. 10A and FIG. 10B are schematic cross sectional views of a magneticstorage element in which an electric current is made directly flowthrough a storage layer to apply a current induced magnetic field.

FIG. 11 is a schematic structural view showing a magnetic storageelement according to another embodiment of the present invention; inwhich FIG. 11A is a cross sectional view of the magnetic storage elementin a major axis direction (direction of an easy axis of magnetization)and FIG. 11B is a cross sectional view of the magnetic storage elementin a minor axis direction (direction of a hard axis of magnetization).

FIG. 12A and FIG. 12B are drawings for explaining methods of recordingdifferent information into the magnetic storage elements shown in FIG.11.

FIG. 13 is a schematic structural view showing a magnetic storageelement according to still another embodiment of the present invention.

FIG. 14 is a graph showing relationship between the time lapsed and atemperature of the storage layer when the wiring directly connected tothe storage layer to make the current flow therethrough.

FIG. 15 is a figure explaining a method to record information on amagnetic storage element of FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining a specific embodiment, a brief summary of the presentinvention will be described. In the present invention, a magneticstorage element in which a first magnetic layer mainly composed of atransition metal and a second magnetic layer mainly composed of arare-earth metal are directly stacked as a storage layer holding arecord by a direction of magnetization is constituted. Furthermore, withregard to the storage layer, a pinned layer is disposed having anon-magnetic layer (a tunnel insulating layer or a non-metal layer, forexample) therebetween.

That is, in the magnetic storage element of the present invention, astorage layer 13 is constituted by directly stacking a first magneticlayer 11 and a second magnetic layer 12. The first magnetic layer 11 ismainly composed of a transition metal (TM) and the second magnetic layer12 is mainly composed of a rare-earth metal (RE). These first magneticlayer 11 and second magnetic layer 12 are directly stacked so that adirection of a magnetic moment (magnetization) M1 of the transitionmetal (TM) of the first magnetic layer 11 and a direction of a magneticmoment (magnetization) M2 of the rear-earth metal (RE) of the secondmagnetic layer 12 are coupled to oppose to each other, that is, to be inanti-parallel. At a room temperature, the directions of themagnetization are as shown in FIG. 3A. In addition, in the presentinvention, at the room temperature, it is arranged so that an amount ofthe magnetization M1 of the first magnetic layer 11 is less than anamount of the magnetization M2 of the second magnetic layer 12, that is,M1<M2 is satisfied. Therefore, at the room temperature, a magnetizationM of the whole storage layer 13 has a direction the same as that of themagnetization M2 of the second magnetic layer 12.

The amount of the magnetization M1 of the transition metal (TM) of thefirst magnetic layer 11 is less affected by temperature change. However,the amount of the magnetization M2 if the rare-earth metal of the secondmagnetic layer 12 decreases as the temperature rises. Therefore, whenheating the storage layer 13 of this structure to have a highertemperature, the magnetization M2 of the rare-earth metal of the secondmagnetic layer 12 (RE) becomes smaller as shown in FIG. 3B. Accordingly,the magnetization M of the whole storage layer 13 becomes smaller thanthat at the room temperature. When heating further to raise thetemperature, as shown in FIG. 3C, the magnetization M2 of the rare-earthmetal (RE) of the second magnetic layer 12 becomes further smaller to bealmost equal to the magnetization M1 of the transition metal (TM) of thefirst magnetic layer 11, that is, M1=M2 is mostly satisfied.Accordingly, the magnetization M of the whole storage layer 13 becomesalmost zero (0). When heating further to raise the temperature more, asshown in FIG. 3D, the magnetization M2 of the rare-earth metal (RE) ofthe second magnetic layer 12 becomes further smaller to be smaller thanthe magnetization M1 of the transition metal (TM) of the first magneticlayer 11, that is, M1>M2 is satisfied. Accordingly, the direction of themagnetization M of the whole storage layer 13 becomes the same as thatof the magnetization M1 of the transition metal (TM) of the firstmagnetic layer 11 and, thus, becomes a reverse direction from thedirection at the room temperature.

It is noted that when the magnetization M1 of the first magnetic layer11 is larger than the magnetization M2 of the second magnetizationlayer, that is, M1>M2 is satisfied, the amount of the magnetization M ofthe whole storage layer 13 increases as the temperature rise by heating.This makes it impossible to reduce the coercive force of the storagelayer 13 even if it is heated and is unfavorable.

In the each state shown in FIG. 3B to FIG. 3D, in comparative of thestate at the room temperature shown in FIG. 3A, the magnetization M ofthe whole storage layer 13 is extremely small so that the coercive forceof the whole storage layer 13 is also small. In the state that themagnetization M of the whole storage layer 13 becomes zero (0) or in astate that the magnetization M of the whole storage layer 13 becomesextremely smaller than the states shown in FIG. 3B or FIG. 3D, thereremain few magnetic anisotropy depending on the shape and influence onthe magnetic field from outside, and influence such as a magneticinteraction between layers, for example, largely affects on the wholestorage layer 13. Therefore, the coercive force of the whole storagelayer 13 is small, but the size of the magnetic field required forcontrolling the direction of magnetization does not become small.

In view of this, in addition to the storage layer 13 of theabove-described structure, as shown in FIG. 4A, a pinned layer 15 isdisposed having a tunnel insulating film 14 or another non-magneticlayer therebetween to constitute the magnetic storage element. And inthe state that the magnetization M of the whole storage layer 13 becomesalmost zero (0) as shown in FIG. 3C or in a similar state, that is, thestate that the magnetization M of the whole storage layer 13 issufficiently small, a magnetic coupling by the magnetic interaction isgenerated between the pinned layer 15 and the storage layer 13. Owing tothe magnetic coupling, it is possible to make the direction of themagnetization M1 of the transition metal (TM) of the first magneticlayer 11 the same as, that is, in parallel with that of a magnetizationM3 of the pinned layer 15. When the magnetic storage element of thisstate is cooled, the direction of the magnetization M1 of the firstmagnetic layer becomes parallel to that of the magnetization M3 of thepinned layer 15, the direction of the magnetization M2 of the secondmagnetic layer 12 becomes anti-parallel to those of the magnetization M1of the first magnetic layer and the magnetization M3 of the pinned layer15, as shown in FIG. 4C, so that the magnetization M of the wholestorage layer 13 becomes anti-parallel to the magnetization M3 of thepinned layer 15.

In order to record information, it is also necessary to make thedirection of the magnetization M of the whole storage layer 13 be inparallel to the direction of the magnetization M3 of the pinned layer,that is, to make the direction of the magnetization M1 of the firstmagnetic layer 11 of the storage layer 13 be in anti-parallel to thedirection of the magnetization 3 of the pinned layer 15. For example, asshown in FIG. 5A, under a condition that the magnetization M of thewhole storage layer 13 after temperature rise becomes smaller than thatat the room temperature, as shown in FIG. 5B, a magnetic field H havinga same direction as the magnetization M3 of the pinned layer may beapplied to realize the above state. The magnetic field H is capable ofinverting the direction of the magnetization M of the whole storagelayer 13 to be the same as the magnetic field H. However, if themagnetization M of the whole storage layer 13 becomes too small, thestorage layer 13 is hardly affected by the magnetic field H as describedabove, it is necessary to keep the temperature not to be high. Recordingin this way enables information recording by changing the direction ofthe magnetization M of the storage layer 13 parallel or anti-parallel tothe magnetization M3 of the pinned layer 15 by use of the magnetic fieldhaving a single direction only.

Next, specific embodiments of the present invention will be described. Aschematic drawing showing a magnetic storage element according toanother embodiment of the present invention is shown in FIG. 1. Thismagnetic storage element 10 comprises the storage layer 13 and thepinned layer 15 structured as described above being disposed having thetunnel insulating layer 14 therebetween to form a magnetic tunneljunction element (MTJ) 16. In the magnetic tunnel junction element (MTJ)16, it is arranged that the horizontal direction in the figure is adirection of an easy axis of magnetization of the magnetic layer andthat the vertical direction in the figure is a direction of a hard axisof magnetization of the magnetic layer. In addition, as a heater forheating the storage layer 13, a resistance heater 21 is disposed on thestorage layer 13. The resistance heater 21 applies an electric currentto the first wiring connected to both ends thereof to generate heat. Thefirst wiring 22 extends in the horizontal direction in the figure to bein parallel to the direction of the easy axis of magnetization of themagnetic layer of the magnetic tunnel junction element 16. Under themagnetic tunnel junction element 16, the second wiring 23 extending inthe vertical direction in the figure (the direction of the hard axis ofmagnetization of the magnetic layer of the magnetic tunnel junctionelement), and the second wiring 23 applies a magnetic field of arightward direction or a leftward direction in the figure whichcorresponds to the easy axis of magnetization of the magnetic layer ofthe magnetic tunnel junction element 16. Under the pinned layer 15, thethird wiring 24 for detecting magnetization is connected. In the figure,a reference numeral 25 shows a substrate on which a transistor and thelike are mounted.

Furthermore, in the magnetic storage element 10 of FIG. 1, a detailedcross sectional view of the vicinity of the magnetic tunnel junctionelement 16 is shown in FIG. 2. As shown in FIG. 2, the storage layer 13has a double-layer structure which comprises the first magnetic layer 11mainly composed of the transition metal (TM) and the second magneticlayer 12 mainly composed of the rare-earth metal (RE) directly stackedthereon. In addition, similarly to the case of FIG. 3A, at the roomtemperature, the magnetization of the first magnetic layer 11 isarranged to be smaller than that of the second magnetic layer 12.Furthermore, the first magnetic layer 11 mainly composed of thetransition metal (TM) is disposed closer to the pinned layer 15 than thesecond magnetic layer 12 so that the tunnel electric current through thetunnel insulating film 14 can be increased. The pinned layer 15comprises a ferromagnetic layer 17 and an anti-ferromagnetic layer 18 tofix a magnetization of the ferromagnetic layer 17 in one directionstacked thereon. A base film 19 under the pinned layer 15 and aprotection film 20 on the storage layer 13 are omitted from FIG. 1.

The first magnetic layer 11 of the storage layer 13 may be composed of atransition metal such as CoFe, and the second magnetic film 12 may becomposed of a rare-earth metal such as Gd. For example, in a case wherethe first magnetic layer 11 is a CoFe film having a thickness of 2 nmand the second magnetic layer 12 is a Gd film having a thickness of 5nm, the magnetization of the second magnetic layer 12 can be larger thanthat of the first magnetic layer 11. The tunnel insulation film 14 maybe an Al₂O₃ film having a thickness of 0.8 nm, for example. In addition,the ferromagnetic layer 17 of the pinned layer 15 may be a Co filmhaving a thickness of 2 nm, for example, and the anti-ferromagneticlayer 18 may be a PtMn film having a thickness of 20 nm, for example.The base film 19 may be a Ta film having a thickness of 10 nm, forexample, and the protection film 20 may be a Ta film having a thicknessof 5 nm, for example.

In the case of the second magnetic layer 12 being the Gd film, since theCurie temperature of the simple Gd is about 300K (about 30° C.), thereis a concern that the magnetization of the second magnetic layer 12disappears because of a usual temperature exceeding the Curietemperature. However, in the present embodiment, since the secondmagnetic layer 12 is directly stacked on the first magnetic layer 11composed of the transition metal so that the magnetization thereof isstable and results in rising of the Curie temperature effectively, andthe magnetization of the second magnetic layer does not disappear at theusual temperature.

In the magnetic storage element 10 of the present embodiment, flowingthe electric current through the first wiring 22 to heat the resistanceheater 21 enables heating of the storage layer 13. In addition, makingthe electric current flow through the second wiring 23 generates thecurrent induced magnetic field and applies the current induced magneticfield to the storage layer 13. The current induced magnetic fieldcontrols the direction of the magnetization of the storage layer 13 tobe either in parallel to or in anti-parallel to the direction of thepinned layer 15 to record information on the storage layer 13. At thetime of recording, by heating the storage layer 13 using the resistanceheater 21, the magnetization M of the whole storage layer 13 becomessmaller than that at the room temperature as shown in FIG. 3A and FIG.3B so that it is possible to record information with a smaller currentinduced magnetic field.

Even if the magnetic storage element 10 constituted as shown in FIG. 1is arranged to change the current induced magnetic field by changing thedirection of the electric current made flow through the second wiring23, similarly to a magnetic storage element used in a usual MRAM, it ispossible to record information. However, such an arrangement results ina drive circuit for feeding the electric current in both directionsthrough the second wiring 23 being more complicated.

Accordingly, in the present embodiment, in the magnetic storage element10 constituted as shown in FIG. 1, using the magnetic coupling betweenthe first magnetic layer (transition metal layer) 11 and the pinnedlayer 15 of the storage layer 13, the direction of the magnetization M1of the first magnetic layer 11 and the direction of the magnetization M3of the pinned layer 15 are made in parallel, similarly to that shown inFIG. 4B. Accordingly, when making the directions of the magnetization M1of the first magnetic layer 11 and the magnetization M3 of the pinnedlayer 15 in parallel, that is, as shown in FIG. 4C, when making thedirections of the magnetization M of the whole storage layer 13 and themagnetization M3 of the pinned layer 15 in anti-parallel, there is noneed to apply a magnetic field and no electric current is required toflow through the second wiring 23. Only required is that making theelectric current through the first wiring 22 to head the storage layer13 by the resistance heater 21.

On the other hand, when making the directions of the magnetization M1 ofthe first magnetic layer 11 and the magnetization M3 of the pinned layer15 in anti-parallel, that is, when making the directions of themagnetization M of the whole storage layer 13 and the magnetization M3of the pinned layer 15 in parallel, the electric current is made flowthrough the first wiring 22 to heat the storage layer 13 by theresistance heater 21 and the electric current is also made flow throughthe second wiring 23 to apply the current induced magnetic field. Atthis time, the direction of the electric current made flow through thesecond wiring 23 is set so that the current induced magnetic fieldgenerated from the electric current works in the same direction as thedirection of the magnetization M3 of the pinned layer 15 with regard tothe storage layer 13. In addition, in order to make the storage layer 13be affected by the current induced magnetic field, setting the amount ofthe electric current made flow through the first wiring 22 to controlthe temperature of the storage layer 13.

In this way, in the present embodiment, it is possible to make theelectric current flowing through the second wiring 23 in only onedirection at the time of recording. Accordingly, in comparative of thecase of flowing the electric current through the second wiring 23 inboth directions, the number of combinations of electrical potentialsupplied to both ends of the second wiring 23 can be reduced and thedrive circuit for supplying the electric current to the second wiring 23can be simplified.

In the magnetic storage element 10 of the present embodiment, detection(reading) of magnetized information recorded on the storage layer 13 canbe carried out similarly to the magnetic storage element used in theconventional MRAM. That is, since resistance against the tunnel currentflowing through the tunnel insulating film 14 changes depending onwhether the directions of the magnetization M of the storage layer 13and the magnetization M3 of the pinned layer 15 are in parallel (samedirection) or in anti-parallel (opposite direction), the magnetizedinformation recorded on the storage layer 13 can be detected from theresistance value or the electric current value.

According to the magnetic storage element 10 of the present embodiment,since it has the storage layer 13 which comprises the first magneticlayer 11 mainly composed of the transition metal and the second magneticlayer 12 mainly composed of the rare-earth metal which are directlystacked and, at the room temperature, the magnetization M2 of the secondmagnetic layer is larger than the magnetization M1 of the first magneticlayer 11, it is possible to change the magnetization M of the wholestorage layer 13 with a relatively small magnetic field by heating thestorage layer so as to make the magnetization M of the whole storagelayer 13 smaller than that at the room temperature.

Since the storage layer 13 and the pinned layer 15 are disposed havingtherebetween the tunnel insulation layer 14, if the magnetization M ofthe whole storage layer 13 is made extremely small by heating thestorage layer 13, it is possible to make the directions of themagnetization M1 of the first magnetic layer 11 and the magnetization M3of the pinned layer 15 be the same without generating the magneticcoupling between the first magnetic layer 11 mainly composed of thetransition metal and the pinned layer 15 and applying the magneticfield.

Accordingly, only by generating heat at the resistance heater 21disposed on the storage layer 13 to heat the storage layer 13, it ispossible to make the directions of the magnetization M1 of the firstmagnetic layer 11 and the magnetization M3 of the pinned layer 15 be thesame even without generating the current induced magnetic field from theelectric current flowing through the second wiring 23. Therefore, itbecomes possible to make the direction of the electric current applyingto the second wiring 23 be only the direction generating the currentinduced magnetic field which makes the directions of the magnetizationM1 of the first magnetic layer 11 and the magnetization M3 of the pinnedlayer 15 oppose to each other, that is, be only one direction, the drivecircuit for supplying the electric current to the second wiring 23 canbe simplified.

A magnetic storage device such as an MRAM can be constituted bydisposing the magnetic storage element 10 of the present embodiment ateach of intersections of a plurality of first wirings 22 and secondwirings 23 orthogonally arranged to be a matrix pattern.

In a case of constituting the magnetic storage device in this way, ifthe electric current is supplied in both directions of the second wiring23 which applies the current induced magnetic field to the storage layer13 of the magnetic storage element 10, it is possible to select anarbitrary magnetic storage element 10 among a number of magnetic storageelements 10 to record information of “0” or “1” by selecting the firstwiring 22 and the second wiring 23 to which the electric current is tobe supplied and selecting the direction of the electric current to flowthrough the second wiring 23.

On the other hand, as described in the above embodiment, when using themagnetic coupling with the pinned layer 15 to set the direction of theelectric current to flow through the second wiring 23, in accordancewith the above steps, an arbitrary magnetic storage element 10 isselected and it becomes impossible to record arbitrary information of“0” or “1”. In such a structure, in order to record arbitraryinformation, the following method can be employed, for example. Here, itis described that generating of the current induced magnetic field byflowing the electric current through the second wiring 23 records theinformation of “0”, and generating of the magnetic coupling with thepinned layer 15 records the information of “1”. In order to record theinformation of “0”, the electric current is supplied to a first wiring22 and a second wiring 23 corresponding to a target magnetic storageelement 10. At this time, the amount of the electric current to besupplied to the first wiring 22 is relatively small. Accordingly, onlythe target magnetic storage element 10 is heated and applied with thecurrent induced magnetic field so that the information of “0” isrecorded. In a magnetic storage element 10 only heated or a magneticstorage element 10 only applied with the current induced magnetic field,the magnetization of the storage layer 13 is not changed and, forexample, if the information of “1” is recorded, the information isretained as it is. In order to record the information of “1”, theelectric current is supplied to a first wiring 22 corresponding to atarget magnetic storage element 10. Here, the amount of the electriccurrent to be supplied to the first wiring 22 is relatively large so asto heat the storage layer 13 to a temperature where the magneticcoupling with the pinned layer 15 works. Accordingly, the magneticcoupling works between the target magnetic storage element 10 and amagnetic storage element 10 corresponding to the same first wiring 22 sothat the information “1” is recorded. In this situation, the informationof “1” is recorded on all the magnetic storage elements corresponding tothe same first wiring 22. Accordingly, information contents stored inthe magnetic storage elements corresponding to the same first wiring 22are read and stored in a different area (for example, in the otherstorage medium or a blank magnetic storage element in the same magneticstorage device) in advance, with regard to the magnetic storage element10 on which the information of “0” was stored, in a step of stopping theelectric current from the first wiring 22 and cooling the magneticstorage element 10, the electric current is supplied to the secondwiring 23 corresponding to the element 10 to apply the current inducedmagnetic field to rewrite the information to be “0”.

Here, in order to measure a temperature change of the magnetizationstate of the storage layer 13 in the magnetic storage element 10 of thepresent embodiment, only two layers of the first magnetic layer 11 andthe second magnetic layer 12 constituting the storage layer 13 wereformed and the temperature change of the magnetization was investigated.As the first magnetic layer 11, a CoFe film having a thickness of 2 nmwas formed, and a Gd film having a thickness of 5 nm was formed as thesecond magnetic layer 12 on the CoFe film and the storage layer 13 wasobtained. While applying a magnetic field of 1 kOe on the storage layer13, the magnetization change of the whole storage layer 13 was measuredwhile changing the temperature.

The measurement result is shown in FIG. 6. The FIG. 6 shows the changeof a ratio (Ms/M0) of a magnetization magnitude Ms based on themagnetization amount M0 at the room temperature by the temperature withregard to the whole magnetization of the storage layer 13. It isconfirmed that the magnetization amount Ms decreases as the temperaturerises, and the magnetization amount Ms becomes minimum, almost zero (0),at around 140° C. That is, the magnetization M1 of the first magneticlayer (CoFe film) 11 and the magnetization M2 of the second magneticlayer (Gd film) 12, which are arranged to be in anti-parallel, becomeequal at the temperature.

Furthermore, in the magnetic tunnel junction element 16 of the structureshown in FIG. 2, relationship between the size of a magnetic field H anda tunnel resistance R was investigated. After having formed the stackedstructure of the magnetic tunnel junction element 16 of the structureshown in FIG. 2, the element 16 is processed to be an oval with a majoraxis of 2 μm and a minor axis of 1 μm and the magnetic field H isapplied in the major axis direction of the element 16. The strength ofthe magnetic field H and the tunnel resistance R of the tunnel currentflowing through the tunnel insulation film 14 was measured. Themeasurement was carried out on the magnetic tunnel junction element 16heated to the room temperature, at 125° C. and 175° C., respectively.

The measurement results are shown in FIG. 7A to FIG. 7C. FIG. 7A shows aresult of the room temperature, FIG. 7B shows a result of 125° C. andFIG. 7C shows a result of 175° C. It is noted that in FIG. 7A to FIG.7C, the magnetic field H is positive when its direction is the same asthat of the magnetization of the pinned layer 15, and negative when itsdirection is an opposed direction.

Here, in each of FIG. 7A to FIG. 7C, during the steps of changing from astate where the resistance value is large to a state where it is small,a value of the magnetic field H at the time the resistance R becomes anaverage of the maximum value and the minimum value is “Hf−Hc”, andduring the steps of changing from a state where the resistance value issmall to a state where it is large, a value of the magnetic field H atthe time the resistance R becomes an average of the maximum value andthe minimum value is “Hf+Hc”. Similar measurements were carried out atthe other temperatures, and FIG. 8 shows the values of Hf and Hc atrespective temperatures. The value Hc becomes zero (0) at around 140° C.and there it changes from positive to negative. Although the value Hf isalso positive at around 140° C. or lower and negative over thetemperature, an absolute value of Hf is large around 140° C.

Here, in a temperature range where the absolute value of Hf is largerthan an absolute value of Hc (|HF|>|Hc|) (around 115° C. to 160° C.),similar to the state of 125° C. shown in FIG. 7B, the magnetizationbecomes stable in a state that the resistance value is small when themagnetic field H does not exist (that is, H=0). In the magnetic tunneljoint element 16 of the structure shown in FIG. 2, similarly to a usualmagnetic tunnel joint element, the tunnel resistance value R becomessmall when the directions of the magnetization M3 of the pinned layer 15and the magnetization M1 of the first magnetic layer (transition metal)11 being in contact with the tunnel insulation film 14 are the same (inparallel), and the tunnel resistance value R becomes large when they arein opposed directions (in anti-parallel).

In other words, it is shown that, in the temperature range of 115° C. to160° C., the tunnel resistance value R is small, that is the directionsof the magnetization M1 of the first magnetic layer (transition metal)11 and the magnetization M3 of the pinned layer 15 of the storage layer13 are the same (in parallel) without applying the magnetic field H.That is, if the storage layer 13 is heated to the temperature and thencooled, as described above, the direction of the magnetization M of thewhole storage layer 13 can be made anti-parallel to that of themagnetization M3 of the pinned layer 15 even without applying themagnetic field.

On the other hand, in order to make the direction of the magnetization Mof the whole storage layer 13 in the reverse direction, as describedabove, the magnetic field H is applied in a condition that the storagelayer 13 is heated to an extent it is still affected by the magneticfield H. The extent that it is still affected by the magnetic field Hmeans a temperature range which almost satisfies |HC|>|Hf| in FIG. 8. Atthis time, in view of FIG. 7A, the storage layer 13 may be applied witha magnetic field H of or over “Hf+Hc”. Heating the storage layer 13makes the value of “Hf+Hc” smaller than that at the room temperature sothat the magnetic field H required for recording becomes smaller.

By the way, in order to further reduce the recording electric current,there may be a case where the magnetic field H to be applied to thestorage layer 13 needs to be further smaller. Therefore, it is arrangedthat the electric current is supplied to the storage layer 13 to changethe magnetization state of the storage layer 13 by the current inducedmagnetic field generated from the electric current. According to thestructure, since the current induced magnetic field works on each of thefirst magnetic layer 11 and the second magnetic layer 12, even without alarger current induced magnetic field, and even if the magnetization(apparent magnetization) M of the whole storage layer 13 becomes smallowing to the temperature rise, the magnetic field can work effectivelyon the magnetic layers 11 and 12 of the storage layer 13. When changingthe magnetization state of the storage layer 13 using the currentinduced magnetic field generated from the electric current supplied tothe storage layer 13, in order to generate a current induced magneticfield in a direction of an easy axis of magnetization of the storagelayer 13, it is necessary to make the electric current flow in adirection of a hard axis of magnetization of the storage layer 13.Therefore, different from the resistance heater 21 and the first wiring22 of FIG. 1, the resistance heater 21 and the wiring for supplying theelectric current are disposed in the direction of the hard axis ofmagnetization of the storage layer 13. For example, a schematic crosssectional view of the magnetic storage element in a case of disposingthe resistance heater 21 in the direction of the minor axis (the hardaxis of magnetization) of the storage layer 13 is shown in FIG. 10A, anda schematic cross sectional view of the magnetic storage element in acase of disposing the wiring 22 connected directly to the storage layer13 in the direction of the minor axis (the hard axis of magnetization)of the storage layer 13 is shown in FIG. 10B.

In this way, change of the magnetization at the time the current inducedmagnetic field is applied by supplying the electric current directly tothe storage layer 13 was investigated. In the magnetic tunnel junctionelement 16 having the structure of FIG. 2, an electrode is attached toan end of the direction of the minor axis of the storage layer 13 sothat the electric current can flow through the storage layer 13. Themagnetization M of the whole storage layer 13 was initialized to have adirection opposed to that of the magnetization M3 of the pinned layer 15by an external magnetic field in advance (similar to the state shown inFIG. 4C). Next, after supplying a pulse current by which a currentinduced magnetic field opposed to the direction of the magnetization M3of the pinned layer 15 to the first magnetic layer 11, whether or notthe magnetization was inverted (the similar state as shown in FIG. 4A)was confirmed using the tunnel resistance R. The measurement was carriedout by setting the pulse width (time) of the pulse current to be thesame and changing the electric current values respectively. As themeasurement result, probability of magnetization inversion PR withregard to the pulse current value i is shown in FIG. 9. The probabilityof magnetization inversion PR shows the probability of inversion bymeasuring 10 pieces of elements by ten times respectively.

As seen from FIG. 9, an assured magnetization inversion can beinvestigated in a range of about 0.7 to 1.1 mA of the pulse currentvalue i. It is noted that the magnetization is not inverted when thepulse current value i is 1.3 mA or more. This is because the electriccurrent value i is large and the temperature of the element furtherrises so that the above mentioned condition of |Hc|<|Hf|. Accordingly,the directions of the magnetization M1 of the first magnetic layer(transition metal layer) 11 and the magnetization M3 of the pinned layer15 in the storage layer 13 becomes the same (the same state as shown inFIG. 4B), and after heated by the pulse current and cooled down to theroom temperature, the directions of the magnetization M of the wholestorage layer 13 and the magnetization M3 of the pinned layer 15 becomeopposed (the same state as shown in FIG. 4C). Thus, as a result, itseems to have no change from the initial state.

It should be noted that in a magnetic storage device such as an MRAM, inorder to integrate the magnetic storage elements at high density, it isnecessary to select a magnetic storage element at an arbitraryintersection of the wirings formed in a matrix pattern orthogonallycrossing and to change the magnetization state thereof. Accordingly,even if the direction of the electric current flowing through the wiring22 set only in one direction, it becomes possible to record informationin accordance with the electric current value.

It should be noted that in a magnetic storage device such as an MRAM, inorder to integrate the magnetic storage elements at high density, it isnecessary to select a magnetic storage element at an arbitraryintersection of the wirings formed in a matrix pattern orthogonallycrossing and to change the magnetization state thereof. However, in acase where the magnetic storage element having a structure as shown inFIG. 10A or FIG. 10B is employed, if it is intended to select anarbitrary magnetic storage element for recording only by supplying theelectric current to the wiring 22, it is required to drive respectivewirings 22 of the magnetic storage element separately so that it resultsin a complicated drive circuit which is not preferable.

Thus, tin order to easily select the magnetic storage element disposedin a matrix pattern, in addition to the wiring for supplying theelectric current to the storage layer, there may be provided a wiringfor heating the storage layer. An embodiment of the magnetic storageelement structured in this way is shown in described in the following.

As another embodiment of the magnetic storage element of the presentinvention, a structure of the magnetic storage element using a pluralityof wirings as a heater is shown in FIG. 11. FIG. 11A shows a crosssectional view of a major axis direction (that is, a direction of aneasy axis of magnetization) of the magnetic storage element, and FIG.11B shows a cross sectional view of a minor axis direction (that is, adirection of a hard axis of magnetization). In the present embodiment,also, the structure of the magnetic tunnel junction element 16 includingthe storage layer 13 is similar to that of the magnetic storage element10 as shown in FIG. 1 before. In a magnetic storage element 40 of thepresent embodiment, a wiring 30 for supplying the electric current to aminor axis direction (a direction of a hard axis of magnetization) of arectangular-formed storage layer 13 is directly connected thereto. Inaddition, a resistance heater 27 for heating the storage layer 13 isdisposed above the storage layer 13 having a slight distancetherebetween and in parallel with a major axis direction (a direction ofan easy axis of magnetization) of the storage layer 13. A wiring 28 isconnected to the resistance heater 27, and the electric current flowsthrough the wiring 28 to the resistance heater 27 to heat it. In thefigure, a reference numeral 26 shows a semiconductor substrate on whichcircuits such as a transistor are mounted.

In the magnetic storage element 40 of the present embodiment, since theresistance heater 27 does not come in contact with the storage layer 13and formed with the slight distance therebetween, the storage layer 13is little affected by the magnetic field from the resistance heater 27.Therefore, the resistance heater 27 does not function as magnetic fieldapplying means, but functions exclusively as a heater. On the otherhand, since a wiring 30 is directly connected to the storage layer 13,when the electric current is supplied to the wiring 30, the storagelayer 13 can be heated by the electric current and a magnetic fieldcorresponding to the direction of the electric current can be applied toeach of the magnetic layers 11 and 12 of the storage layer 13. That is,the wiring 30 functions as a heater as well as magnetic field applyingmeans.

A magnetic storage device can be constructed by arranging the magneticstorage element 40 vertically and horizontally to be a matrix pattern,and bonding the wiring 28 for resistance heating and the wiring 30 forsupplying the electric current to the storage layer 13 at the magneticstorage elements 40 positioned on the same line or the same row thereof.Accordingly, the magnetic storage device capable of easily selecting themagnetic storage element 40 at an intersection of two wirings 28 and 30can be constituted.

Next, a method for recording information on the magnetic storage element40 of the present embodiment will be described with reference to FIG. 11and FIG. 12. Here, in a state that the magnetization of the wholestorage layer 13 is in the same direction as that of the magnetizationof the pinned layer 15, information of “0” is recorded, and in a opposedstate, information of “1” is recorded. The direction of the electriccurrent supplying to the storage layer 13 from the wiring 30 is set to adirection applying the current induced magnetic field in the directionopposed to the magnetization of the pinned layer 15.

First, as shown on the left side of FIG. 12, in a case where a pulsecurrent P1 is supplied to the resistance heater 27 before a pulsecurrent P2 to be supplied to the storage layer 13, the electric currentflows through the resistance heater 27 by the pulse current P1 andheating by the resistance heater 27 is first carried out. Then, heatingand application of a magnetic field are carried out by the pulse currentP2. Since the temperature of the storage layer 13 rises owing to theheating by the resistance heater 27 by the pulse current 1 and, in astate once heated, the magnetic field is applied, influence of themagnetic field to the storage layer becomes small owing to thetemperature rise, and the first magnetic layer 11 and the pinned layer15 are once magnetically coupled so that the directions of themagnetization of the first magnetic layer 11 and the magnetization ofthe pinned layer 15 become parallel. Thereafter, the electric current ofthe pulse current P1 runs out first and in that state there is still thepulse current P2, at the time when the temperature lowers, the currentinduced magnetic field by the electric current from the wiring 30 isapplied. Accordingly, the direction of the magnetization of the firstmagnetic layer (transition metal layer) 11 becomes opposed to that ofthe current induced magnetic field, that is, the magnetization of thepinned layer 15, and further, when being cooled down to the roomtemperature, the magnetization of the second magnetic layer 12 whichopposes to the magnetization of the first magnetic layer 11 becomesstrong so that the direction of the magnetization of the whole storagelayer 13 becomes the same as that of the magnetization of the pinnedlayer 15. In this way, the information “0” is recorded.

On the other hand, as shown in the right side of FIG. 12, in a casewhere the pulse current P1 is supplied to the resistance heater 27 afterthe pulse current P2 to be supplied to the storage layer 13, heating andapplication of the magnetic field are carried out with the pulse currentP2 and, then, heating with the pulse current P1 is carried out. Sincethe temperature of the storage layer 13 rises owing to the heating withthe pulse current P2 and further with the pulse current P1, influence ofthe magnetic field to the storage layer 13 becomes small owing to thetemperature rise, and the first magnetic layer 11 and the pinned layer15 are magnetically coupled so that the directions of the magnetizationof the first magnetic layer 11 and the magnetization of the pinned layer15 become parallel. Thereafter, the electric current of the pulsecurrent P2 runs out first and in that state there is still the pulsecurrent P1, at the time when the temperature lowers, the current inducedmagnetic field by the electric current from the wiring 30 is notapplied. Accordingly, the direction of the magnetization of the firstmagnetic layer (transition metal layer) 11 is still the same (parallel)to that of the magnetization of the pinned layer 15, and further, whenbeing cooled down to the room temperature, the magnetization of thesecond magnetic layer 12 which opposes to the magnetization of the firstmagnetic layer 11 becomes strong so that the direction of themagnetization of the whole storage layer 13 becomes opposed to that ofthe magnetization of the pinned layer 15. In this way, the information“1” is recorded.

Therefore, by shifting the timing of the two pulse currents P1 and P2,in correspondence with the sequential order of the pulse currents P1 andP2, the direction of the magnetization of the storage layer 13 can bechanged and, as a result, information of “0” or “1” can be recorded.

According to the magnetic storage element 40 of the present embodiment,the magnetization state of the storage layer 13 can be changed usingonly the electric current having one direction to be supplied to thewiring 30. Accordingly, in comparative of a case of supplying theelectric current in both directions to the wiring 30, the number ofcombinations of electrical potential to be supplied to the both ends ofthe wiring can be reduced. For example, it is only necessary to set oneto be high potential or the both to be the same potential, and it is notrequired to set one to be low potential and the other to be highpotential. Therefore, when a large number of magnetic storage elements40 are integrated to have a magnetic storage device, the drive circuitfor supplying the electric current to the wiring can be simplified andit is easy to integrate the elements at high density.

By supplying the electric current from the wiring 30 directly to thestorage layer 13 to apply the current induced magnetic field, thecurrent induced magnetic field effectively works on the storage layer13. Accordingly, in comparative of a case of applying the currentinduced magnetic field from the wiring 23 which is away from the storagelayer 13 as shown in FIG. 1, recording with less recording current ismade possible. Since the storage layer 13 can be heated to have thehigher temperature with the electric current flowing from the wiring 30to the storage layer 13, the current induced magnetic field can beapplied in a state that the coercive force of the storage layer 13 issmaller than that at the room temperature, and the current inducedmagnetic field required for recoding can be smaller. From thisviewpoint, recording with smaller recording electric current is madepossible.

Furthermore, since the storage layer 13 is heated by supplying theelectric current from the wiring 30 directly to the storage layer 13 andalso by supplying the electric current from the wiring 28 to theresistance heater 27, it is possible to select and record on a magneticstorage element at an arbitrary position among a number of magneticstorage elements arranged in a matrix pattern.

In the above embodiment, information recording is performed by changingthe pulse currents P1 and P2 to be supplied to the two wirings 28 and 30by shifting their timing. However, it is also possible to carry outrecording in another method. A specific embodiment thereof will bedescribed below.

A schematic structural view showing a magnetic storage element accordingto still another embodiment of the present invention is shown in FIG.13. As shown in FIG. 13, a pulse current Ip is supplied to the storagelayer 13 which comprises the first magnetic layer 11 and the secondmagnetic layer 12 in a magnetic storage element 50, and, using thecurrent induced magnetic field H generated from the pulse current Ip, amagnetic field is applied to the storage layer 13. A direction of thepulse current Ip is set so that the current induced magnetic field Hworks in a direction opposed to the magnetization M3 of the pinned layer15 with regard to the first magnetic layer (transition metal layer) ofthe storage layer 13. In order to supply the pulse current Ip to thestorage layer 13 in this way, similarly to the wiring 30 of FIG. 11B,the wiring may be connected directly to the minor axis direction(direction of the hard axis of magnetization) of the storage layer 13 sothat the pulse current Ip flows from the drive circuit to the wiring.Since, in the case where the current induced magnetic field is appliedby supplying the electric current directly from the wiring to thestorage layer 13, the current induced magnetic field is applied in acondition that the coercive force of the storage layer 13 becomes smallowing to the temperature rise by heating with the electric current.

Relationship between the temperature of the storage layer 13 and Hc, Hfhas a tendency as shown in FIG. 8 before. As the temperature rises, Hcdecreases and Hf increases, and when the temperature reaches a certaintemperature Tx, Hf becomes larger than Hc. When the wiring is directlyconnected to the storage layer 13 and the electric current is suppliedthereto, as shown in FIG. 14, after a lapse of a certain time t_(x), thetemperature reaches Tx where Hf>Hc is satisfied, and thereafter, thetemperature rise slows down and is saturated at a certain temperature.

In the magnetic storage element 50 of the present embodiment, using thechange shown in FIG. 14, by making the pulse width of the pulse currentIp longer than or shorter than the time t_(x), information recording iscarried out in the following way.

Here, in a state that the magnetization of the whole storage layer 13 isin the same direction as that of the magnetization of the pinned layer15, information of “0” is recorded, and in a opposed state, informationof “1” is recorded. At first, when the pulse width of the pulse currentIp is made shorter than the time t_(x), the temperature of the storagelayer 13 only reaches under the temperature Tx, and the current inducedmagnetic field H with the pulse current Ip is applied to the storagelayer 13 in that state. Accordingly, the direction of the magnetizationM1 of the first magnetic layer 11 becomes anti-parallel with thedirection of the magnetization M3 of the pinned layer 15 in accordancewith the influence of the current induced magnetic field H. And when thepulse current Ip finishes and the storage layer 13 is cooled down to theroom temperature, the magnetization M2 of the second magnetic layer 12opposing to the magnetization M1 of the first magnetic layer 11 becomesstrong so that the direction of the magnetization M of the whole storagelayer 13 becomes the same as that of the magnetization M3 of the pinnedlayer 15. In this way, the information “0” is recorded.

On the other hand, when the pulse width of the pulse current Ip is madelonger than the time t_(x), the temperature of the storage layer 13reaches the temperature Tx or over, and the current induced magneticfield H with the pulse current Ip is applied to the storage layer 13 inthat state. Accordingly, since the magnetic coupling with themagnetization M3 of the pinned layer 15 becomes stronger than theinfluence of the current induced magnetic field H, the direction of themagnetization M1 of the first magnetic layer 11 becomes parallel to thatof the magnetization M3 of the pinned layer 15. And when the pulsecurrent Ip finishes and the storage layer 13 is cooled down to the roomtemperature, the magnetization M2 of the second magnetic layer 12opposing to the magnetization M1 of the first magnetic layer 11 becomesstrong so that the direction of the magnetization M of the whole storagelayer 13 becomes anti-parallel with that of the magnetization M3 of thepinned layer 15. In this way, the information “1” is recorded.

Therefore, by making the pulse width (time) of the two pulse current Iplonger than or shorter than t_(x), the direction of the magnetization ofstorage layer 13 can be changed and, as a result, information of “0” or“1” can be recorded.

According to the magnetic storage element of the present embodiment,similarly to the above-mentioned embodiment, the magnetization state ofthe storage layer 13 can be changed using only the electric current Iphaving one direction. Accordingly, the number of combinations ofpotentials to be supplied to the both ends of the wiring to make thecurrent Ip flow therethrough can be reduced in comparative of a case offlowing the electric current in both directions of the wiring.Therefore, when a number of magnetic storage elements 50 are integratedto have a magnetic storage device, the drive circuit can be simplifiedand it is easy to integrate the elements at high density.

Even in the magnetic storage element of the present invention, if it isarranged that the electric current is supplied from the wiring directlyconnected to the storage layer 13 to heat the storage layer 13, and,similarly to FIG. 11A, the electric current is supplied to the otherwiring orthogonally crossing with the wiring to heat the storage layer13, it is possible to selectively record information on a magneticstorage element at an arbitrary position among a number of magneticstorage elements positioned in a matrix pattern by selecting the wiringto which the electric current is to be supplied from respectiveplurality of two kinds of wirings orthogonally crossing.

It is noted that in the magnetic storage element of each of the aboveembodiments, instead of the tunnel insulation film 14, a non-magneticconductor layer such as a Cu layer may be used between the storage layer13 and the pinned layer 15 to constitute a giant magnetoresistiveeffective element (GMR element) so that it is possible to read arelative magnetization of the storage layer 13 and the pinned layer 15on the basis of the giant magnetic resistive effect of the GMR element.The magnetic tunnel junction element 16 using the tunnel insulation film14 has a large resistance change rate and can detect the magnetizationso that it is effectively advantageous for simplifying the magneticstorage element and the magnetic storage device.

The present invention is by no means limited to the above-describedembodiments, and other various configurations are allowable withoutdeparting from the essential spirit of the present invention.

1-6. (canceled)
 7. A magnetic storage device comprising: a magneticstorage element comprising a storage layer for holding a magnetizationstate as information, a non-magnetic layer and a pinned layer in which adirection of the magnetization is fixed, which are stacked, said storagelayer is composed of a first magnetic layer mainly composed of atransition metal and a second magnetic layer mainly composed of arare-earth metal which are directly stacked; in which a magnetizationamount of said first magnetic layer is smaller than that of said secondmagnetic layer at a room temperature; a reader for reading out arelative magnetization between said storage layer and said pinned layerdepending on a change of an electrical resistance; a first wiring forapplying a current induced magnetic field having one direction to saidstorage layer, said first wiring electrically connected to said storagelayer; a second wiring to said magnetic storage element in addition tosaid first wiring; and a heater for heating said storage layer, theheater comprising the first wiring and the second wiring.